Portable cervical traction device using constant force springs

ABSTRACT

A compact cervical traction apparatus having a carriage which is slidably disposed over a base, the carriage carrying a head support band. A pair of springs that provide a uniform traction force over the entire range of carriage movement are enclosed within a spring housing at the rear of the base. The springs are constant force springs and an uncoiled portion of the first spring is disposed below an uncoiled portion of the second spring. The uncoiled portion of the first spring is attached to a Z-shaped member having an elongated trailing end that is mounted to the carriage so as to bias the carriage. The uncoiled portion of the second spring is attached to a lip member that is disposed to securely fit within the Z-shaped member and thereby combine the traction force of the second spring to that of the first spring. An L-shaped disengaging plate has a portion which passes between the uncoiled portions of the springs proximate attachment of the lip member to the Z-shaped member. The disengaging plate also has a cam surface portion. Pressure applied to the cam surface portion causes the disengaging portion of the plate to separate the lip member and the Z-shaped member sufficiently to prevent coupling. Such pressure is selectively supplied by a cam pivotably secured to the spring housing. The constant force springs each provide a traction force of four pounds to the carriage.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of application Ser. No.662,333, filed Oct. 17, 1984, now U.S. Pat. No. 4,606,333 which is acontinuation-in-part of Ser. No. 585,361, filed Mar. 1, 1984, now U.S.Pat. No. 4,593,684.

TECHNICAL FIELD

The invention relates to a portable traction device.

BACKGROUND ART

Vertebral problems of the cervical spine sometimes require the relief ofexcessive intervertebral pressure. Traction is required to elongate thecervical spine to release this pressure. The most commonly used methodis to have the patient seated with a neck or chin strap to which tensionis applied through a rope over a pulley with a weight attached. The chinstrap stresses the temporomandibular joint with possible pain anddeformity of the joint. The chin strap immobilizes the jaw and preventstalking. Since the head weighs approximately ten pounds, this weightmust be exceeded before any effective elongation of the cervical sectioncan take place.

Other procedures employ straps which are wrapped around the head at theoccipital area and also use a forehead strap to hold the head. Thepressure of tension across the forehead and temple require moreelaborate harness straps. A chin and head strap require auxiliarysuspension points, such as a door.

Traction devices for a reclining patient are known. U.S. Pat. No.4,593,684 to applicant discloses a portable traction device whichengages the occipital region of the back of the skull. U.S. Pat. No.4,166,459 discloses a traction device which uses a sliding carriage witha raised preshaped yoke which engages the neck. An elastically biasedcarriage holding the yoke applies force. The unit must be attached to amattress for anchoring.

An object of the present invention is to devise a portable cervicaltraction apparatus which is self-contained and used without supportequipment, such as a door. Another object of the invention is to devisesuch an apparatus which provides a force that remains the same evenafter a change of positioning by the subject.

DISCLOSURE OF THE INVENTION

The objects have been met by a compact cervical traction unit whichprovides a constant force over its entire range of movement. Theconstruction includes a horizontal base having a forwardly disposedmovable carriage on which is mounted a brace that supports a flexibleband for engaging the occipital region of the skull. A pair of springsprovide a force to the movable carriage.

A first constant force spring is coiled atop the rear portion of thehorizontal base. The axis of the coil extends perpendicularly to theplane of carriage movement. An opening in the base accepts a free end ofthe first constant force spring so that the free end may be braced underthe base and toward the front portion of the base for attachment to thecarriage. A second constant force spring is mounted directly in front ofthe first spring, whereby a free end of the second spring may passthrough an opening in the base and then toward the carriage, directlyatop the uncoiled portion of the first constant force spring. A lipmember attached to the free end of the second constant force spring isdisposed to be selectively secured to a Z-shaped member attached to thefree end of the first spring. When the lip member is attached to theZ-shaped member, the combined force of the springs is applied to thecarriage. Preferably, the springs each provide a constant force of fourpounds. The range of carriage movement may be as great as three feet.

An L-shaped disengaging plate has a cam surface portion that extendsparallel the plane of carriage movement, adjacent the constant forcesprings. The disengaging plate further has a disengaging portion whichpasses between the uncoiled portion of the springs proximate theattachment of the lip member to the Z-shaped member. A pivoting cammember is disposed atop the rear portion of the carriage to apply forceto the cam surface portion of plate, pressing the disengaging portiondownward to separate the lip member from the Z-shaped member, therebyreleasing the carriage from biasing contact with the second constantforce spring.

Additional constant force springs may be applied to the assembly andselectively attached to the carriage in the same manner as the secondconstant force spring. While it is not necessary that additional springshave a force of four pounds, it has been discovered that the four poundincrements supplied by the first and second springs are advantageousand, in actuality, supply the only forces necessary in the treatment ofthe majority of vertabral problems of the cervical spine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective front view of the cervical traction apparatus ofthe present invention.

FIG. 2 is a side view of the apparatus of FIG. 1 showing the apparatusin use.

FIG. 3 is a partial cutaway view of the spring assembly of FIG. 1.

FIG. 4 is a side view of the spring assembly of FIG. 4.

FIG. 5 is a bottom view of the apparatus of FIG. 1.

FIG. 6 is an exploded perspective view of the cervical traction deviceof FIG. 1.

FIG. 7 is a cross-sectional view of the apparatus taken along lines 7--7of FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

With reference to FIG. 1, cervical traction apparatus 11 has a flatelongated base 13 that is horizontally disposed. The base has dimensionsof approximately 20 inches long, seven and one-half inches wide, andone-half inch deep. A carriage 15 with dimensions ten inches long andseven and one-half inches in width is mounted so as to move horizontallyback and forth just over the base in the directions of arrows A and B.

Mounted near the forward end of the carriage 15 is a head cradleassembly 16 consisting of a metal brace 17 having two upwardly extendingside arms 19 and 21 with a head supporting band 25 connectedtherebetween. The side arms are about three inches high and about sevenand one-half inches apart from each other, and have the taut, wideflexible band 25 anchored through narrow slots 30 in each side arm andfastened by screws 32. The side arms of the brace are of a trapezoidshape. Due to the angle of the slots 30, the band 25 lies in a tiltedposition at an angle between 30° and 60° from the horizontal, therebyfacing toward the rear of carriage 15. The band has a thickness ofapproximately three-sixteenths inches and a width of two inches. Thehead supporting band is made of a resilient elastomeric material such assilicone rubber and has an optimum durometer measurement of 45-55d whichflexes to fit to the shape of the occipital area of the skull when theback of the head is placed in the head support. An elastic strap 26 isdisposed beneath band 25 for added support.

Operation of the cervical traction apparatus of the present inventionmay best be understood with reference to FIG. 2. The neck of a user islowered toward the elastomeric band 25. On contact with the band, theband begins to fold and shape itself to the natural lordotic curve.Then, as the neck is lowered to full contact and traction is applied inthe direction of arrow C, the effect of the downward weight of the neckand the pull of the traction is to apply pressure on the lower side ofthe occipital bone. This permits the traction effect along the entirecervical spine. The band is thus in a position to be securly seated andcan act as a fulcrum. The head can be tipped forward or backward asneeded to work with the user's normal lordotic curve, without losing thesecure position on the band.

The force which is applied to the head causes the supporting unit tomove forward. This is overcome in the invention by an anchor pad 27.During traction a reclining patient's back rests on the anchor pad whichmay be made of foam on metal covered with durable material, similar to athin canvas pillow. The anchor pad is approximately the same width asthe base 13 and may be of varying lengths but, preferably, the pad isshorter than the base to permit it to be folded under the base. Theentire apparatus, when folded, may be compactly stored and suspendedfrom hanger 34.

With reference to FIG. 3 traction forces are applied to move thecarriage 15 by means of a spring system having two constant forcesprings 35, 37. Constant force springs 35, 37 are each coiled about anaxis 39, 41, as shown by arrows D and E. The coils are enclosed within ahousing 43 and are constructed to provide a constant force of fourpounds each over the entire range of carriage movement. The constantforce springs may be obtained from Walker Spring Co. of Sante FeSprings, Calif.

Typically, springs obey Hook's Law. That is, as a spring is extended,the spring will exert an increasingly greater force to return to arelaxed position. Constant force springs, on the other hand, exert auniform force irrespective of the amount of spring extension. A user ofthe present invention may therefore periodically stretch the neck ormake slight changes in body position without concern of increasing ordecreasing the traction force.

FIG. 3 illustrates the traction apparatus having only the first constantforce spring 35 providing traction force to the carriage 15. The freeend 45 of the first spring passes through an opening in the portion ofthe base below the spring. The free end is attached to a Z-shaped member47. The Z-shaped member has an elongated trailing end 48 that is mountedto the carriage 15. Spacers 49 distance the Z-shaped member from thecarriage. As the carriage is moved in the direction indicated by arrowF, the first spring 35 provides a constant traction force of four poundsto the head cradle assembly.

The second constant force spring 37 also has a force of four pounds andthis force may be added to that of the first spring 35. The secondspring has a free end 51 which is attached to a lip member 53. FIG. 4best illustrates the construction and the interaction of the lip member53 and the Z-shaped member 47. The lip member is attached to the freeend 51 of the second spring by a rivet 55. Likewise, the Z-shaped memberis mounted to the first spring by means of a rivet 57 or a spot weld.The elongated trailing end 48 of the Z-shaped member is held to thespacer 49 and the carriage by a screw 59 and nut 61 arrangement. The lipmember is aligned to abut the vertical portion 63 of the Z-shaped memberand to make contact with the elongated trailing end 48 when the carriageis moved in the direction of arrow F of FIG. 3. In this manner thecombined force of the two springs is applied to the carriage.

As can be seen in FIGS. 3 and 4, a disengaging portion 65 of a L-shapeddisengaging plate 67 passes between the free ends 45, 51 of the springs.The disengaging plate 67 has a cam surface portion 69 that is secured tothe base 13 by a screw 71 and nut 73 arrangement. The cam surfaceportion has a separation that is ramped upward to form a cam surface 75.Downward pressure, indicated by arrow G, on the disengaging plate 67will place the disengaging portion into a lowered position 65'. As aresult, the Z-shaped member 47' is situated so that it will not makecontact with the lip member 53. That is, the second constant forcespring 37 will not be in biasing contact with the carriage when thedisengaging plate portion is in position 65'.

The disengaging plate 67 is forced downward by a cam 77 having aprojection 79. The cam is pivotally mounted to the spring housing 43 atpivot point 81. When the cam is oriented vertically the cam projection79 forces the ramped cam surface 75 downward, thereby causing themisalignment of the lip member 53 with respect to the Z-shaped member47'.

FIG. 5 is a bottom view of the base 13. The base contains a channel 83that is sufficently wide to permit horizontal movement of the carriagewithout interference from the screws 59 or spacers, not shown, thatretain the elongated trailing end 48 of the Z-shaped member to thecarriage. The free end 45 of the first spring provides a constant forceof four pounds to the carriage. Screws 85 secure the spring housing tothe base.

As shown in FIG. 6, carriage 15 rides on the surface of base 13 by meansof three wheels 89, 91, and 93. Wheel 89 is set under the middle of therear of carriage 15 and wheels 91 and 93 are set under opposite cornersof the carriage front. Both the base and the carriage are formed withdownturned edges which serve to protect the wheels under the carriage.The channel 83 is defined between two parallel protective rails 95, 97which extend lengthwise along the midline of the bottom surface of thebase. Spacers 49 run in the channel 83 and contact posts 98. Washers 99are disposed on each side of the spacers 49. By this means the carriageis slideably mounted on the base.

In operation, FIG. 7 shows that the apparatus has a locking mechanism 87that secures the carriage 15 in a position furthermost from the springhousing 43. When the head of the user is comfortably postioned, the userdisengages the pivotal locking mechanism from a receptacle mounted onthe base. In position 87' the carriage is free to slide so that theforce from the springs provide traction force to the head cradleassembly 16 in the direction of arrow H.

Both springs will be in biasing contact with the carriage when the cam77 is in a horizontal position. In this position the cam is out ofcontact with the cam surface 75 leaving the disengaging plate 67 high,thereby aligning the Z-shaped member 47 for contact with the lip member53. The lip member will be engaged by the Z-shaped member when thecarriage is moved away from the spring housing 43.

Only the first constant force spring will be in biasing contact with thecarriage when the cam is pivoted into a vertical position. With the camin a vertical position the disengaging plate is held low by theprojection 79 of the cam. The disengaging plate will thus hold theZ-shaped member below the lip member, preventing the second constantforce spring from combining with the first spring to provide tractionforce to the carriage.

The illustrated arrangement shows utilization of only two constant forcesprings. Additional constant force springs may be employed. However, thetwo springs, each furnishing four pounds of force, are sufficient forthe treatment of the majority of vertebral problems of the cervicalspine. The uniform force of the springs over the entire range ofcarriage movement is critical. The constant force springs permit apatient to periodically change positions or stretch muscles withoutunintentionally varying the traction force. The arrangement adds to thecomfort and safety of the apparatus.

The entire unit weighs approximately three pounds. The base and carriagemay be molded from a plastic such as an ABS resin. These are lightweight, have good impact strength, and are dimensionally stable andresistant to most oils and chemicals. The brace for the head cradle maybe steel, aluminum or plastic. The head band should preferably be ahypo-allergenic material such as a silicone rubber of a thickness togive a good support to the occipital area.

I claim:
 1. A portable cervical spine traction apparatus comprising,aflat elongated support base adapted to be horizontally disposed andhaving front and rear portions, a carriage slideably mounted on thefront portion of said base, said carriage having a means for engagingthe back of the skull, and a spring means for biasing said carriagerearwardly relative to said support base, said spring means mounted tothe rear portion of said base and having a first and a second constantforce spring, connectable together for increasing bias by predeterminedamounts of force, said first constant force spring being attached tosaid carriage and said second constant force spring being selectivelyengaged to said first constant force spring, and release means fordisengaging said second constant force spring from said first constantforce spring, said release means having a cam and a disengaging plate,said disengaging plate having a cam surface portion and a portionpassing between said constant force springs, said cam capable ofexerting force on said disengaging plate, thereby separating said secondconstant force spring from said first constant force spring.
 2. Theapparatus of claim 1 wherein said second constant force spring has a lipmember and said first constant force spring has a Z-shaped member toselectively lock said second constant force spring to said firstconstant force spring.
 3. The apparatus of claim 1 wherein each constantforce spring provides a four pound force to bias said carriagerearwardly.
 4. The apparatus of claim 1 wherein said means for engagingthe back of the skull includes a resilient elastomeric support band forengaging the occipital region by elastomeric flexing.
 5. A portablecervical spine traction apparatus comprising,a planar support basehaving a planar carriage mounted for slideable motion thereon and meansfor limiting the relative motion of the base and carriage to linearmotion, a head support mounted to the carriage, biasing means forproviding a uniform biasing force over the entire range of carriagemotion, said biasing means including first and second constant forcesprings mounted to said support base, said constant force springs eachcoiled about an axis extending perpendicularly to said motion of thecarriage, each spring having an uncoiled portion, said constant forcesprings aligned so that said uncoiled portion of said first constantforce spring is parallel to and directly below said uncoiled portion ofthe second constant force spring, at least one constant force springbeing attached to said carriage, and locking means for selectivelylocking said uncoiled portions of said springs to each other, saidlocking means including a lip member and a z-shaped member, saidz-shaped member attached to the uncoiled portion of said first spring,said lip member attached to the uncoiled portion of the second springand disposed to engage the z-shaped member, said means for selectivelylocking said uncoiled portions further including a means for selectivelyseparating said lip member and said z-shaped member.
 6. The apparatus ofclaim 5 wherein said means for selectively separating said lip memberfrom said z-shaped member includes a cam and a disengaging plate, saiddisengaging plate having a cam surface portion and a disengagingportion, said disengaging portion extending between said uncoiledportions of said springs, said cam capable of exerting force on said camsurface portion, thereby spacing apart said uncoiled portions.
 7. Theapparatus of claim 5 wherein each constant force spring provides a fourpound force to bias said carriage.
 8. The apparatus of claim 5 whereinsaid head support includes a rigid brace having two upwardly extendingarms supporting a resilient elastomeric band for engaging the occipitalregion of the skull.